Parsing binary stream interface application example pack, unpack, ord function usage_PHP tutorial

At work, I also gradually learned how powerful pack, unpack, and ord are for binary byte processing. Below I introduce them one by one. In our work, they are probably not used much. In my most recent job, I needed to use binary streams for communication, and then the interface was received using PHP. When I was processing it, I looked up a lot of information. Because they are rarely used, and few friends use them at work. At work, I also gradually learned how powerful pack, unpack, and ord are for binary byte processing. Below I introduce them one by one.
pack function description: This function is used to compress and pack data into a string.
Syntax: pack(format,args+)
Parameter Description
format required. Specifies the format used when packaging data.
args+ optional. Specifies one or more parameters to be wrapped.
Character description
a Fill the string blanks with NULL characters
A Fill the string blanks with SPACE characters (spaces)
h Hexadecimal string, Low byte first
H Hexadecimal string, high byte first
c Signed character
C Unsigned character
s Signed short integer (sixteen digits, according to the computer's bit order)
S Unsigned short integer (sixteen digits, according to computer bit order)
n Unsigned short integer (sixteen digits, in order of the high order)
v Unsigned short integer (sixteen digits, in order of the high order) Low-order order)
i Signed integer (according to computer order and range)
I Unsigned integer (according to computer order and range)
l Signed long integer (32 digits, according to Computer bit order)
L Unsigned long integer (32 digits, according to computer bit order)
N Unsigned short integer (32 digits, high order order)
V Unsigned short Integer (32 digits, low-order order)
f single precision floating point number (according to the range of the computer)
d times precision floating point number (according to the range of the computer)
x empty
X inverse Return one digit
@ Fill in the NULL character to the absolute position
unpack function description: This function is used to decompress the data of the string of digits
Syntax: unpack(format,args+)
Parameter description
format is required. Specifies the format used when packaging data.
args+ optional. Specifies one or more parameters to be wrapped.
The parameters are the same as pack.
ord function description: Returns the acill code value of the corresponding character
Syntax: ord($character);
Example description:

Copy code The code is as follows:

//A character
$str=(pack ("A*", "China"));
echo $str,"=",strlen($str),"byte n";
getAscill($str);
//H Character
$str=(pack("H*", "fffe"));
echo $str,"=",strlen($str),"byte n";
getAscill($ str);
//C character
$str=(pack("C*", "55","56","57"));
echo $str,"=",strlen ($str),"byte n";
getAscill($str);
//i character short integer 32 bits 4 bytes 64 bits 8 bytes
$str=(pack( "i", "100"));
echo $str,"=",strlen($str),"byte n";
getAscill($str);
//s characters are short Shape 2 bytes
$str=(pack("s", "100"));
echo $str,"=",strlen($str),"byte n";
getAscill($str);
//l character long integer 4 bytes
$str=(pack("l", "100"));
echo $str,"=",strlen ($str),"byte n";
getAscill($str);
//f character single precision floating point 4 bytes
$str=(pack("f", "100 "));
echo $str,"=",strlen($str),"byte n";
getAscill($str);
//d character double precision floating point 8 words section
$str=(pack("d", "100"));
echo $str,"=",strlen($str),"byte n";
getAscill($str );
function getAscill($str)
{
$arr=str_split($str);
foreach ($arr as $v)
{
echo $v," =",ord($v),"n";
}
echo "=============rnrn";
}
?>

Through the above example, we can see that the same string, stored in different formats, occupies a different number of bytes. You can also see here that saving characters in different formats can save storage space. And the encryption effect is unreadable. Suddenly something occurred to me, the problem of designing database field types, if a field is only: a 10-bit length integer. We set it to an integer: 256*256*256*256, which is 4 bytes. If it is set to a string of 10 lengths. That takes up 10 bytes. The entire digestive space is doubled. Setting the correct character type can help a lot to improve database performance. Haha, I'm a bit off topic...
Analysis of examples of php processing bytecode communication
The function of pack just mentioned: saving space, encrypted format
The following is an example of these two, interface development requirements:
Parameter description
Username 20 bytes, character type
Password 10 bytes, character type
Age 1 byte, unsigned char type
Date of birth 4 bytes, integer type (19800101)
Email 50 bytes, string
Use between each field: "

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At work, I gradually learned how powerful pack, unpack, and ord are for binary byte processing. Below I introduce them one by one. In our work, they are probably not used much. I recently...